1. Field of the Invention
The present invention relates to the preparation of potatoes, and more specifically, the preparation of intermediate-moisture potatoes that may be stored on the shelf for extensive time periods without the need for refrigeration.
It is well known in the prior art that potatoes may be dehydrated, but extensive problems have resulted in producing a final product that has high quality from consumer considerations. Flavor loss from the processing steps has caused lower quality than is desired. Additionally, storage of the dehydrated product may necessitate specific conditions such as refrigeration, including freezing. Upon rehydration, non-uniform water absorption in the product may result which also lowers product quality.
A recent development in the food industry is the emphasis on intermediate-moisture foods which have the ability of being stored and marketed in a substantially non-refrigerated condition. These foods were designed to avoid the need to be packaged in a hermetically sealed container and commercially sterilized or maintained in a frozen or refrigerated state throughout the period of distribution and storage by the consumer.
The intermediate-moisture foods are based on the principle of reducing the availability of water in the food for microbial growth. The availability of water for the germination and microbial growth is closely related to its relative vapor pressure, commonly designated as water activity. It was found that the use of a wide variety of water-soluble solutes, or osmotic agents, has the effect of depressing the water activity of the foods to levels at which most bacteria will not grow.
The water activity of a food is defined as the partial pressure of water in the food divided by the saturation pressure of water at the temperature of the food. The water activity can be determined by placing a sample in a container which is then sealed, and after equilibrium is reached, determining the relative humidity above the sample. Most products of the intermediate-moisture type have between 10 to 40% moisture, and a water activity between 0.65 and 0.9.
2. Discussion of the Prior Art
U.S. Pat. No. 4,390,550 is directed to intermediate-moisture foods that are frozen for long term preservation and which remain shelf-stable for a long period after thawing. The foods are prepared with a sugar/water ratio of 1:1 which reduces the water activity to between 0.75 to 0.93, preferably between 0.80 and 0.90. The sugar is employed as the principal source of water-soluble solutes in a range of 30% to 60% of the composition. Other non-sugar, water-soluble solutes may also be included with the sugar, such as sodium chloride, potassium chloride, glycerol, propylene glycol and the like. The method of making these foods include blending 15 to 45% water, sugar in a sugar/water ratio of 2-1:1, 2.5 to 30% fat and minor amounts of salt, emulsifier, stabilizer and flavoring, provided that the solubles are adequate to provide a water activity of 0.8 to 0.9, pasteurizing the mixture and cooling the resultant products. The pasteurizing is performed by heating and holding the mixture at 180.degree. F. for 5 minutes. The mixture is then homogenized, packaged and frozen. In one example, fruit is added to the mixture. The fruit is first infused with sugar solutes to reduce its water activity to 0.45 to 0.65. Infusion is achieved by placing the fruit in a hot bath of fructose-containing syrup at about 220.degree. F. to 225.degree. F. for about 5 minutes. Although disclosed as being useful for many diverse foods, there is no disclosure of a process for making shelf-stable potatoes or other starch-based foods.
U.S. Pat. No. 3,881,028 is directed to a method for preparing intermediate-moisture, shelf-stable potatoes that includes preparing strips of potatoes, blanching the potatoes at about 212.degree. F., thereafter soaking the blanched potatoes in a heated (180.degree. F.) salt solution, such as a 1.5% sodium chloride solution, drying by microwave heating for 45 seconds, frying in oil at 350.degree. F. for 6 minutes and drying in a microwave for 75 seconds. The shelf-stable potatoes are reconstituted by soaking in tap water at 140.degree. F. for 10 minutes and then heated in an oven at 425.degree. F. for 7 minutes. The salt dip is employed to remove surface starch to reduce non-uniformity caused by the blanching.
U.S. Pat. No. 4,751,093 discloses a process for preparing french fries for freezing that includes infusing low molecular weight soluble solids, such as 2%-20% sodium chloride, simultaneously with blanching at about 200-205.degree. F. for 8 minutes, drying at up to 200.degree. F., frying in oil at about 350.degree. F. for 1 minute and freezing.
There is a need for a fast and simple process for preparing shelf-stable intermediate-moisture potatoes without case hardening that when reconstituted and cooked have firm texture and excellent flavor.